Space heating is a component of heating, ventilation, and air conditioning (HVAC) and is a predominant mode of conditioning space. Depending on the local climate, space heating is in operation up to and beyond seven months out of the year. During the time of such operation, there will be numerous occasions when cooling of the space will be needed to prevent discomfort and lost productivity of inhabitants of such space. Thus, the adjustability of HVAC systems is desirable. Space heating has traditionally been accomplished by two-pipe systems that incorporate a hot water boiler.
One approach to improve the adjustability of HVAC systems is shown by U.S. Pat. No. 4,360,152, which discloses an auxiliary heating system for reducing fuel consumption of a conventional forced-air heating system. A boiler tank substantially filled with water is connected by hot and cold water lines to a heat exchanger disposed within the cold air duct of the forced-air heating system. A firebox which extends into the boiler tank is adapted to receive combustible material such as wood for heating the water in the tank. A pump directs hot water from the tank through the hot water line to the heat exchanger whereby cool air moving through the cold air duct is preheated as it passes through the heat exchanger. Heating tubes in communication with water in the boiler tank may extend through the firebox for supporting logs therein. Additional heating tubes may extend through a flue directed upwardly from the firebox through the boiler tank. A disadvantage to the '152 disclosure is that requires the installation of an additional component to the existing HVAC system.
Another approach directed at the adjustability of HVAC systems is shown in U.S. Pat. No. 6,769,482, which discloses a HVAC device that includes both heating and cooling operating modes. The '482 disclosure provides an interface for selecting the operating parameters of the device. The interface allows the input of a set point temperature at which the HVAC device conditions the ambient temperature of a space. A mode switch-over algorithm uses the set point temperature, the sensed temperature from the conditioned space, and prestored threshold values that depend on the device's operating capacities, to determine when to change the device between heating and cooling modes. Within each of the respective modes, a heating or cooling algorithm controls the engaging and disengaging of the heating and cooling elements of the device to maintain the temperature of the conditioned space within a desired comfort zone. The '482 patent does not address the diverse and localized needs within large spaces, such as where a large space will require cooling in one area and heating in another area.
The use of variable speed pumps for control of HVAC systems has been adopted in U.S. Pat. No. 5,095,715, wherein an integrated heat pump and hot water system provides heating or cooling of a comfort zone, as required, and also provides water heating. As a power management feature, the speed of a variable speed compressor is reduced to a predetermined fraction of its normal operating speed, in response to a demand limit signal provided from the electric power utility during times of peak electrical load. A reference compressor speed is computed based on the current compressor speed, indoor temperature, outdoor temperature, and zero-load temperature difference. If the system is between operating cycles when the demand limit signal is received, a stored speed is used which corresponds to the compressor speed at a predetermined outdoor-indoor temperature difference. The '715 disclosure fails to address the diverse and localized needs within large spaces, such as where a large space will require cooling in one area and heating in another area.
Notwithstanding these efforts, the prior art fails to improve the functionality and adjustability of HVAC systems to meet today's needs of energy conservation and quick changeover from heating to cooling in a space and of being able to provide heating and cooling at the same by the same system.
Accordingly, there is a need in the art for an improved HVAC system that can use water in an efficient manner, for instance from both the cooling side and boiler side of a space heating configuration. Because of the higher costs of the construction of new buildings, there is also a need for an improved HVAC system that will be able to be retrofitted to existing spaces at a cost that is less than the installation of an entirely new HVAC system. There is also a need for an adjustable system that offers simultaneous cooling and heating, depending on the need of the particular subunit of the space in which the HVAC operates.